I was just thinking about things...
You could just mold one piece of kydex to create the half of a holster that will provide holding pressure for the gun, while the other half could be leather.
Perhaps the leather could be the 'outside' that the public sees showing from your pocket.
Mold the kydex to the correct side of the gun it will mate to in your pocket.
Make a paper pattern for the leather piece and size it so it's tight enough to just allow the gun to be holstered.
You'll need to figure that part out so the gun is snug but easy enough to draw when needed.
Once you've got your two pieces (leather and kydex) cut, you want to put them together.
To stitch the two together, you just figure out the size of holes you need for the stitching/thread, use a dremel or some other drill and drill your holes in the kydex first.
Use the drilled kydex as a pattern through which an awl/nail/needle can be passed to make your stitch marks on the leather.
Open the holes in the leather just big enough to push your needle through without the thread being loose.
I used waxed thread. I've had my spools for many years now from the days I did more leather stitching.
You could use Dacron fishing line, Kevlar thread, anything with some strength.
If you look close enough at my first picture, you'll see the belt loop is stitched closed this way, although it is one piece of kydex.
Another idea might be to make a simple pocket like an Uncle Mike's pocket
www.gunaccessories.com/UncleMikes/InsideThePocketHolsters.asp. I have one for my S&W 642.
Before you stitch up the material, maybe you could create a kydex band that would help with providing a snugger fit if you wish.
You just give it some molding to fit the gun and stitch the kydex to the material.
I found out that when shaping kydex around the trigger guard, I had to keep from pressing too much material into the trigger space.
I saw that too much material in the wrong place might 'grab' the trigger when reholstering and fire off a round at a most inappropriate time!